Resource sharing in relay operations within wireless communication systems

ABSTRACT

A wireless communication relay terminal including a controller coupled to a transceiver wherein the controller is configured to cause the transceiver to transmit a first portion of a first sub-frame during a first time-frequency region to a wireless communication device, to cause the transceiver to receive, from a base station, a portion of a second sub-frame during a second time-frequency region wherein the first and second time-frequency regions are non-overlapping The controller is also configured to detect a control region within the portion of the second sub-frame received by attempting to decode information in a possible control region of the second sub-frame having at least one of several possible starting locations that are known a priori by the terminal.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wireless communications andmore particularly to resource sharing in wireless communication systemshaving a base station that communicates with mobile terminals via arelay.

BACKGROUND

Traditionally in cellular networks, a base station (BS), (e.g., Node-Bor eNB) communicates directly with end user equipment (UE) within thecoverage area of the BS (denote these UE as UE1). In relay operations, aRelay or a relay terminal or a Relay Node (RN) first receivesinformation from an eNB on an eNB-to-RN link and then sends out thereceived information intended for UE that are within the coverage areaof the RN (denote these UE generically as UE2 where it is understoodthat multicasting to a more than one UE's is incorporated). For an“in-band” RN that receives from an eNB on the same band as occupied bythe eNB-to-UE1 link, the eNB-to-RN link needs to share resources in timeand frequency (or some fraction thereof) with the eNB-to-UE1 link.Conventionally when there is only regular eNB-to-UE1 communications,each UE1 typically receives a control message to determine whatresources are allocated to the UE1 and the location of the allocatedresources. An RN could, for example, behave like a regular UE (UE1) toreceive control message from eNB at the same time when eNB transmitcontrol message to UE1. However, an RN may not be able to receive thecontrol message from the eNB if the RN needs to transmit controlinformation to UE2, at the same time when eNB is transmitting controlinformation to UE1 and the RN.

In the context of the Release-8 specification of Long Term Evolution(LTE) system developed by third generation partnership project (3GPP)that is based on Orthogonal Frequency Division Multiplexing (OFDM) fordownlink transmissions, the eNB-to-UE1 link consists of typically 1˜3OFDM symbols at the beginning of each 1-ms sub-frame for controlchannel, i.e., PDCCH, transmissions. Typically an OFDM symbol comprisesof an integer number of time units (or samples), where a time unitdenotes a fundamental reference time duration. For example, in LTE, thetime unit corresponds to 1/(15000×2048) seconds. Thus, the PDCCHtransmissions are a first control region with a fixed starting location(contemporaneously) at the first OFDM symbol in a sub-frame. All theremaining symbols in a sub-frame after the PDCCH are typically fordata-carrying traffic, i.e., PDSCH, assigned in multiples of ResourceBlocks (RBs). Typically, an RB comprises of a set of subcarriers and aset of OFDM symbols. The smallest resource unit for transmissions isdenoted a resource element which is given by the smallest time-frequencyresource unit (one subcarrier by one OFDM symbol). For example, an RBmay contain 12 subcarriers (with a subcarrier separation of 15 kHz) with14 OFDM symbols with some subcarriers being assigned as pilot symbols,etc. Typically, the 1 ms sub-frame is divided into two slots, each of0.5 ms. The RB is sometimes defined in terms of slot rather thansub-frame. According to the Release-8 specification, the uplinkcommunication between the UE1 and eNB is based on Single-CarrierFrequency Division Multiple Access (SC-FDMA), which is also referred toas Discrete Fourier Transform (DFT)-spread OFDM. Typically, the RN toeNB uplink communication may also be preferably done using SC-FDMA. Avirtual resource block is a resource block whose subcarriers aredistributed (i.e., non-contiguous) in frequency, whereas a localized RBis an RB whose subcarriers are contiguous in frequency. Virtual RB mayhave improved performance due to frequency diversity. Release-8 UEstypically share resources in the frequency domain (i.e., on an RB-levelor in multiples of an RB) rather than in time in any individualsub-frame on the downlink. Similarly, the eNB-to-RN link may also shareresources with the eNB-to-UE1 link in the frequency domain (i.e., on anRB-level or in multiples of an RB). A problem may then occur where theRN is transmitting a PDCCH to its users, i.e., UE2, at the beginning ofeach sub-frame, making the RN unable to receive the PDCCH transmitted bythe eNB at the same time.

The various aspects, features and advantages of the disclosure willbecome more fully apparent to those having ordinary skill in the artupon careful consideration of the following Detailed Description thereofwith the accompanying drawings described below. The drawings may havebeen simplified for clarity and are not necessarily drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a wireless communication system.

FIG. 2 illustrates a relayed communication link.

FIG. 3 is a schematic block diagram of a relay node.

FIG. 4 illustrates a sub-frame having first and second control regions.

FIG. 5 illustrates an alternative sub-frame having first and secondcontrol regions.

FIG. 6 illustrates a first sub-frame transmitted by an eNB and a secondsub-frame transmitted by a relay node.

FIG. 7 illustrates a frame structure for uplink and downlink FDD with 1ms sub-frames labeled 0 to 9 with a 10 ms Radio Frame.

FIG. 8 illustrates possible starting points and possible size for secondcontrol region for a first group of RNs (RN1) and a second group of RNs(RN2).

FIG. 9 illustrates a first sub-frame transmitted by an RN on thedownlink with a control region and a second sub-frame transmitted by aneNB comprising of a first control region, and a second portion of secondsub-frame showing possible starting points and possible size for secondcontrol region for a first group of RNs (RN1) and a second group of RNs(RN2).

DETAILED DESCRIPTION

In FIG. 1, a wireless communication system comprises one or more fixedbase infrastructure units 100 forming a network distributed over ageographical region. The base units may also be referred to as an accesspoint, access terminal, base, base unit, base station (BS), Node-B,eNode-B, eNB, Home Node-B, relays, relay terminal or relay node (RN), orby other terminology used in the art. The base units are generally partof a radio access network (RAN) that includes one or more controllerentities communicably coupled to one or more corresponding base units.The RAN is generally coupled to one or more core networks, which may becoupled to other networks, like the Internet and public switchedtelephone networks, among others. These and other elements of the accessand core networks are not illustrated but are known by those havingordinary skill in the art.

In FIG. 1, the one or more base units serve a number of remote units 110within a serving area, for example, a cell or a cell sector via awireless communication link 112. The remote units may be fixed units ormobile terminals. The remote unit may also be referred to as asubscriber unit, mobile, mobile station (MS), user terminal, subscriberstation, user equipment (UE), terminal, relay node (RN), relay, or byother terminology used in the art. In some deployments, the relay or RNmay also be considered as a part of the radio access network (RAN),serving one or more remote units while wirelessly connecting to one ormore base units to access one or more core networks.

In FIG. 1, generally, the base units 100 transmit downlink communicationsignals to serve remote units in the time and/or frequency domain. Theremote units communicate directly with the one or more base units viauplink communication signals. Some remote units 106, 108 and 110communicate with the base unit 100 via relay 102. The one or more baseunits may comprise one or more transmitters and one or more receiversfor downlink and uplink transmissions. The remote units may alsocomprise one or more transmitters and one or more receivers.

In some implementations, there are instances where the RN is unable toreceive a control message from the eNB when the RN transmits controlinformation to UE2 at the same time that the eNB is transmitting controlinformation to UE1, including the RN. Under these circumstances, the RNmust get its allocation information from the eNB on a different controlchannel located with a different time-frequency resource or accessmethod (e.g., a different temporal location, different frequencylocation, different time-frequency location or using a different spatialsignature (e.g., beam-forming vector)) within the sub-frame or the slot.According to one aspect of the disclosure, the RN is configured todetect the location and size of resources assigned for the eNB-to-RNlink dynamically. This includes the case where such a link is notprovisioned in a particular frame to handle the case where there is notraffic through the RN. The resources used for the eNB-to-RN link aregenerally scaled with the total traffic needs of all UE2 under the RN'scoverage area. For example, in the extreme case where there is no UE2currently being served through the RN, in theory, no resources arerequired by the eNB-to-RN link. In other words, the associated controloverhead in this case could be minimized or even adjusted to zero sothat all resources are made available for the eNB to serve UE1.Generally, the eNB-to-UE1 link and eNB-to-RN link, which includescontrol and data transmissions, may be multiplexed so that totalresources are efficiently shared among UE1 and one or more RN accordingto the dynamic traffic needs of UE2.

FIG. 2 illustrates an exemplary relay link between a Macro eNB 200 and aUE2 204 via a relay 202. In the example, the downlink (DL) resources areco-frequency or adjacent in frequency. The uplink (UL) resources may beconfigured similarly.

In FIG. 3, a wireless communication infrastructure entity 300, forexample, an eNB, comprises a transceiver 310 coupled to a controller320. In one embodiment, the controller is coupled to memory 330 and isembodied as a programmable digital controller capable of executingsoftware of firmware code stored in memory. The code configures thecontroller to perform functionality discussed more fully below.Alternatively, the controller may be implemented as a hardwareequivalent of the exemplary digital controller or as a combination ofhardware and software.

The controller includes sub-frame generation functionality 322.Generally the controller generates multiple sub-frames that constitute aframe, which may constitute part of a super-frame. In 3GPP LTEimplementations, the sub-frame is an OFDM time-frequency resource. Insome system architectures, users do not receive a portion of thesub-frame that includes a control region. In the scenario discussedabove, for example, the RN is incapable of receiving at least some partof a control region having a fixed starting location in a portion of thesub-frame when the RN is required to simultaneously transmit to a UE2during some part of the control region. Thus in some embodiments, thecontroller is configured with functionality 324 that generates asub-frame having a first control region for a first set of users and asecond control region (SCR) for a second set of users wherein the secondset of users may not, in some instances, be able to receive the firstcontrol region. The first set of users may be UE1 and the second ofusers may be one or more RNs. In a more particular implementation, thefirst control region has a fixed starting location within the sub-frameand the second control region has a starting location that is one ofseveral possible starting locations within the sub-frame. The lattercontrol region may be thought of and referred to as a floating controlregion. In each sub-frame, the base station controller locates thefloating control region in any one of the possible locations, which maybe determined by the relay node as discussed more fully below.

The location of floating control region, when it is assigned withnon-zero resources, is configured to start from a limited set ofpossible points within the sub-frame. The set of possible startinglocations of the floating control region may be determined as a functionof several variables, including parameters that are RN-specific oreNB-specific and some other physical parameters such as modulation andnumber of resources. In the exemplary 3GPP LTE implementation, thestarting location is defined in both the frequency and time domain. Inanother example, the possible starting locations may be defined by a setof Resource Blocks that are determined as a function of RN-RNTI or asspecified by a configuration message, in each RB, the starting locationmay be given by the Resource Element with the smallest Subcarrier indexand smallest OFDM symbol index. The control region size may be definedas set of REs.

Typically, the control region comprises the control information aboutthe downlink control information (DCI) formats or scheduling messagesthat may inform the RN of the modulation and coding scheme, transportblock sizes, time-frequency resources, pre-coding information,hybrid-ARQ information, RN Identifier, and other control informationthat is required to decode the downlink data transmissions and enableuplink data transmissions.

In FIG. 3, at 326, the controller includes functionality that causes thetransceiver to transmit the one or more sub-frames to the first andsecond set of users (e.g., UE1 and RN, respectively). In someembodiments where the sub-frame includes a second control region thathas a starting location that is one of several possible startinglocations within the sub-frame, the controller and more generally thebase station may transmit the sub-frame without signaling the actualstarting location of the floating control region in the sub-frame.

The starting locations of the floating control region may be eitherpre-defined in a fixed way or according to some higher-layerconfiguration message sent to the relay nodes or terminals. Generally,the several possible starting locations of the floating control regionare known a priori by the receiving terminal, for example, a relay, thatfor whatever reason is incapable of receiving the first control regionbefore decoding. In some implementations, at 328 in FIG. 3, thecontroller is configured to cause the transceiver to signal the severalpossible starting locations of the floating control region to the relaywithout signaling the actual starting location of the floating controlregion. The signaling of the possible starting locations of the floatingcontrol region by the base station may be explicit or implicit and mustoccur prior to the decoding of the sub-frame by the RN. For example, thebase station can send a configuration message via high layers to informan RN of the possible starting locations of the floating control region.The configuration message can be sent during initial system setup or asa dedicated Radio Resource Configuration (RRC) message. Theconfiguration message can also be sent via broadcast control or thecommon control channel or the system information broadcast. Theconfiguration message may also be sent via semi-persistent or persistentscheduling wherein the RN listens to the message at pre-determinedtime-frequency resources. In yet another approach, the configurationmessage can be dynamically signaled via the Physical Downlink ControlChannel (PDCCH). The explicit signaling of possible locations enablesthe base station to adjust the set of possible locations if needed. Forexample, an eNB may decide to reserve a certain set of RBs for eNB to RNcontrol region and due to backwards compatibility reasons, the eNB maynot be able assign portions of RBs that used for eNB to RN control tosupport a Release-8 UE1. By explicit signaling of the possiblelocations, the eNB may be able to dynamically adjust the resourcesrequired for the eNB-RN communication based on the traffic served andnumber of RNs. For example, if the eNB is serving a single RN, it may beable to assign a smaller number of RBs as possible starting locations toreduce the number of decoding attempts required by the RN. Thus in FIG.3, the signaling of the possible starting locations may occur prior totransmission of the sub-frame for which the starting locationinformation is required. In other implementations, the relay may obtaininformation on the possible locations from some other source. In oneexample, the possible starting locations are fixed and defined in astandard specification according to a pre-determined rule. In anotherexample, the set of possible starting locations is not fixed orexplicitly signaled. Instead, it can be derived implicitly according toan algebraic rule with variable parameters such as the Radio NetworkTemporary Identifier (RNTI) of the RN and other parameters as specifiedby the eNB. Other information signaled by the base station or otherwiseobtained by the relay node, and more generally user terminals, includesmodulation order, coding rate, coding format, among other information.This information may also be signaled in a higher-layer configurationmessage or otherwise obtained by the relay node or other terminal towhich it pertains.

According to a related aspect of the disclosure, the base stationcontroller is configured to generate the floating control region havinga fixed size or a variable size or dimension that is known to the relaynode, wherein the base station does not convey the dimension of thesecond control region to the relay node. Generally, the several possibledimensions of the floating control region are known a priori by thereceiving relay terminal that for whatever reason is incapable ofreceiving the first control region. In some implementations, at 328 inFIG. 3, the base station controller is configured to cause thetransceiver to signal the several possible dimensions of the floatingcontrol region to the relay terminal without signaling the actual sizeor dimension of the second control region. The signaling of the possibledimensions of the floating control region may be explicit or implicit.Similar to the explicit signaling of possible starting locations of thefloating control region, the base station can send a configurationmessage via high layers to inform an RN of the possible sizes of thefloating control region. The configuration message can be sent duringinitial system setup or as a dedicated RRC message or via commonbroadcast message (SIB) or via semi-persistent or persistent scheduledmessage or using dynamic signaling on the PDCCH. The explicit signalingof possible dimensions will allow the base station to adjust the set ofpossible dimensions if needed. In other implementations, the relay mayobtain information on the possible control region dimensions from someother source. In one example, the possible dimensions are fixed anddefined in some standard specification. In another example, the set ofpossible dimensions is not fixed but not explicitly signaled either.Instead, it can be defined implicitly according to a certain rule andparameters such as the Radio Network Temporary Identifier (RNTI) of theRN. When scheduling resources for an RN, the scheduler in an eNB mayutilize the channel quality information (CQI) feedback from the RN orother means to determine an appropriate control channel startinglocation and dimension to be utilized from a possible starting locationsand dimensions.

The location of floating control region, when it is assigned withnon-zero resources, is configured to start from a limited set ofpossible points. The set of possible starting locations of the floatingcontrol region may be determined as a function of several variables,including some parameters that are RN-specific or eNB-specific and someother physical parameters such as modulation and number of resources. Inthe exemplary 3GPP LTE implementation, the starting location is definedin both the frequency and time domain. In another example, the possibledimensions may be defined as a set of multiples of REs, (e.g.,{1,4,10,12,36,72,144}) and with a given set of starting locations, e.g.,given by the Resource Element with the smallest Subcarrier index andsmallest OFDM symbol index, in a set of RBs. Once the possibledimension(s) and starting location(s) are known, the REs may beenumerated in a time-first or a frequency-first manner (or in anotherpre-determined fashion) to form the possible control region. The set ofpossible control regions may also be referred to as a search space, asthe RN will search this set of possible control regions to find anyassignments for itself. Typically the decoding procedure includes acyclic-redundancy check (CRC) code for detection of successful decoding.RN can use existing Reference Signals that are transmitted from eNB. Thecontrol region may also contain reference signals that can be commonReference Signals (CRS) and also possibly dedicated reference signals(DRS), if predefined, for control channel decoding. The ReferenceSignals are pilots or known waveforms that are transmitted to aidchannel estimation and decoding. Since the eNB to RN link may experiencebetter channel conditions than a typically mobile UE1, the eNB-RN linkmay be enhanced by having much more efficient control region (e.g. usinghigher order modulations such as 16-QAM, or 64-QAM) and different RSstructures to support the eNB to RN communication. For instance, theconfiguration message may indicate a varying pilot density or RSstructure based on the mobility of RN. For example, a first set of RNsthat are fixed (e.g., on top of a building) might be supported with onetype of RS structure (e.g., smaller pilot density) whereas a second setof RNs that are mobile (e.g., on top of a bus, etc) may be supportedwith another type of RS structure (e.g., higher pilot density).Typically, the RB that contains a control region for UE2 may not beallocatable as part of a resource allocation for a Release-8 UE1 andtherefore any remaining resources (i.e., REs) in the RB might beallocated to the RN as a resource allocation. Since the RN decodes thepossible control region in the RB, the RN may be able rate-match anddetermine correctly the resources allocated for its resource allocation.When using localized RB for eNB-to-UE1 link, the eNB scheduler has theflexibility to schedule RN and UE1 traffic according to theirfrequency-selective fading conditions. When using virtual RB foreNB-to-UE1 link, eNB may still reserve one or more RB Groups (RB Groupsof 4 RBs) for RNs.

In one implementation, the base station controller is configured togenerate the first control region to convey information for resourceallocations within a traffic region of the sub-frame to a first set ofusers, wherein the first control region and the traffic region aremultiplexed temporally. The controller is also configured to generatethe second or floating control region to convey information for resourceallocations within the traffic region of the sub-frame to the second setof users. In one application, the first set of users is a set ofsubscriber terminals and the second set of users is one or more relaynodes. The first and second control regions may be generally multiplexedtemporally. In one implementation, the second control region and thetraffic region are multiplexed temporally. In another alternativeimplementation, the second control region and the traffic region aremultiplexed in frequency. In yet another alternative implementation, thesecond control region and the traffic region are multiplexed in time andfrequency.

In FIG. 4, a sub-frame 400 having time-frequency resources comprises afirst control region 410 that has a fixed starting location and may ormay not have a fixed dimension. The first control region is temporallymultiplexed with a data traffic region 420. In one embodiment, the firstcontrol region includes scheduling messages that allocate data trafficregion resources to the first set of users. In FIG. 4, for example, thefirst control region allocates resources 422 to the first set of users.The sub-frame 400 also comprises a second control region 430 that istemporally multiplexed with the first control region. The second controlregion includes scheduling messages that allocate data traffic regionresources to the second set of users. For example, the second controlregion allocates resources 424 to the relay nodes. The second controlregion is frequency multiplexed with the data traffic region resources.As discussed, the second control region is a floating control regionhaving a starting location that is one of several possible startinglocations known a priori to the relay node. Thus the second controlregion may be located elsewhere in the data traffic region.

In FIG. 5, a sub-frame 500 having time-frequency resources comprises afirst control region 510 that has a fixed starting location and may ormay not have a fixed dimension. The first control region is temporallymultiplexed with a data traffic region 520. The first control regionincludes scheduling messages that allocate data traffic region resources522 to the first set of users. The sub-frame 500 also comprises a secondcontrol region 530 that is temporally multiplexed with the first controlregion. The second control region includes scheduling messages thatallocate data traffic region resources 524 to one or more relay nodes.The second control region is multiplexed in frequency and time with thedata traffic region resources and may be located in one of severalpossible starting locations that are known a priori to or by the relaynode.

A wireless communication terminal for example, a relay node (RN),comprises a transceiver coupled to a controller. In one embodiment, thecontroller is coupled to memory and is embodied as a programmabledigital controller capable of executing software of firmware code storedin memory. The code configures the controller to perform functionalitydiscussed more fully below. Alternatively, the controller may beimplemented as a hardware equivalent of the exemplary digital controlleror as a combination of hardware and software.

The RN transceiver is configured to receive, in at least some instances,only a portion of a sub-frame transmitted by a network base station, forexample, by an eNB. The sub-frame transmitted by the base stationincludes a first control region with a fixed starting location withinthe sub-frame and second control region, wherein a starting location ofthe second control region is at one of several possible startinglocations within the sub-frame. The portion of the sub-frame received bythe RN, however, excludes at least a portion of the first controlregion.

The RN controller includes decoding functionality wherein the controlleris configured to detect the second control region within the portion ofthe sub-frame received by attempting to decode information in a possiblecontrol region having at least one of the several possible startinglocations. As noted, the RN controller has a priori knowledge of thepossible starting locations prior to decoding and of the size orpossible sizes of the floating control region. Thus the controller may“blindly” detect the floating control region by attempting to decodeinformation in the received sub-frame beginning at the possible startinglocations. The decoding information conveyed in the floating controlregion, performed at the RN under different control region hypotheses,may also require the necessary parameters about the transmission formatincluding modulation order, types of coding, and its rate. Theseparameters may be known a priori before any decoding attempt. Inembodiments where the size of the floating control region varies fromone sub-frame to the next, the controller is configured to detect thefloating control region by attempting to decode information based on oneof several possible sizes that are known a priori by the relay terminal.Decoding is simplified in embodiments where the control region has aknown fixed dimension. As suggested above, the possible startinglocations and size or possible sizes of the floating control region maybe communicated to the relay node in a higher-layer message or by othermeans. Other information known generally by the RN controller prior todecoding may include generally includes modulation order, coding rate,coding format, among other information.

Thus generally, the floating control region or channel of the eNB-to-RNlink sub-frame contains control messages to all RNs associated with theeNB. The starting location of the control channel within the sub-frameis pre-defined (via RN-specific search space and/or RN-common searchspace or a search space that is common to a group of RNs) and the sizeof control channel in terms of occupied resources is limited to a set ofvalues or is fixed. Each RN blindly decodes the control channel based onall hypotheses, i.e., the known possible starting locations and size(s)of the control regions. Upon successful blind detection, the RN willlearn about any resource is assigned and the location and size. Sincethe RN is required to blindly detect zero or non-zero resources occupiedby the control channel of the eNB-to-RN link, the base station has moreflexibility to serve UE1 by assigning any of the remaining resources.Also, for instances where there is no eNB-to-RN traffic, the eNB canprovide all resources to UE1. No control signaling overhead is requiredinforming the RN since the RN uses blind detection to obtain resourceassignments.

Thus in some instances the relay terminal controller is configured tocause the transceiver to transmit a first portion of a first sub-frameduring a first time-frequency region to a wireless communication deviceand to cause the transceiver to receive, from a base station, a portionof a second sub-frame during a second time-frequency region wherein thefirst and second time-frequency regions are non-overlapping. In oneembodiment, the first and second time-frequency regions are separated bya time interval. In another embodiment, the first and secondtime-frequency regions are an integer number of OFDM symbols. In anotherembodiment, the first and second time-frequency regions are an integernumber of time units.

In one embodiment, the first sub-frame is a multimedia broadcastmulticast over a single frequency network sub-frame. In the exemplaryLTE implementation, the first portion of the first sub-frame includes aphysical downlink control channel (PDDCH). The portion of the firstsub-frame includes a first control region having scheduling messages. Insome embodiments, the first sub-frame is a non-unicast sub-frame. Inother embodiments, the first and second sub-frames are separate from asub-frame containing a paging channel transmitted by the terminal. Inthe exemplary embodiment, the portion of the second sub-frame includes asecond control region corresponding to the possible control regionhaving scheduling messages. In some embodiments, the portion of thesecond sub-frame includes a data region that is distinct intime-frequency from the second control region.

The relay terminal controller is configured to detect a control regionwithin the portion of the second sub-frame received by attempting todecode information in a possible control region of the second sub-framehaving at least one of several possible starting locations that areknown a priori by the terminal. The controller is also configured todetect the second control region within the portion of the sub-framereceived by attempting to decode information in the possible controlregion having a dimension that is also known a priori by the terminal.In some embodiments, the relay terminal decodes the possible secondcontrol region in a time interval non-overlapping a time intervalcorresponding to the first control region.

FIG. 6 illustrates a first 3GPP LTE-specific sub-frame 600 transmittedby an eNB comprising a PDCCH 602 and a control channel 604 for an RN.FIG. 6 also illustrates a second sub-frame 610 transmitted by a relaynode with a PDCCH 612 and a switch gap 614. The 1-3 symbols of eachsub-frame are allocated to the physical downlink control channel (PDCCH)targeted to UE1, e.g., subscriber terminals. Whenever the RN isexpecting DL data from the eNB in a second sub-frame, RN signals to theUE2 that the first sub-frame is a special sub-frame or a non-unicastsub-frame and hence the UE2 may read only the first one or two (orpossibly zero) OFDM symbols from the RN DL transmission on the secondsub-frame. RN may be able to transmit “blank”, “empty” or “notranmission” in the rest of the first sub-frame. The blank or empty maycomprise not transmitting any reference signals or control or data. Itmay also be noted that the rest of the first sub-frame may include someadditional transmissions for some reserved purposes such as preambletransmission, etc. It is can be seen that the RN can receive the DLtransmission from the eNB and search the possible second control regionto find data for the RN. The characterization of the sub-frames as afirst sub-frame and a second sub-frame are used here although the twosub-frames may occur contemporaneously to indicate that these twosub-frames represent the downlink transmissions from two different cellsor cell sites or entities, one is associated with the eNB and another isassociated with the relay. While FIG. 6 represents a frequency divisionmultiplexing (FDM) of control and data within the eNB-to-RN linksub-frame, time division multiplexing (TDM) is also possible. In the FDMcase, the total number of RE available for the floating control channelin each sub-frame over a sub-band of 12 subcarriers, including CRS, areN*11 symbols*12 subcarriers=N*132 REs, where is N is the number ofpossible starting locations (or RBs in this example). The RN may berequired to buffer the sub-frame prior to decoding so there may beadditional latency compared with TDM control channel. However, such anadditional processing latency may be tolerable because typicallyRN-reception frames may have low duty cycle given that the RN also needsto transmit in other frames. In the case of TDM control, the size ofcontrol in time domain could be a fraction of the sub-frame (e.g., 4symbols in the first slot, or 7 symbols in the second slot). In thefrequency domain, the number of occupied sub-carriers could be madeequal to the occupied bandwidth of the entire eNB-to-RN link. This valueis an integer number of 12 subcarriers which may also be detected by theRN. It is noted that either TDM or FDM control or a combination of bothwithin eNB-to-RN link can be supported.

PDCCH contains the control information about the downlink controlinformation (DCI) formats or scheduling messages, which inform the UE ofthe modulation and coding scheme, transport block size and location,precoding information, hybrid-ARQ information, UE Identifier, etc thatis required to decode the downlink data transmissions. This controlinformation is protected by channel coding (typically, acyclic-redundancy check (CRC) code for error detection and convolutionalencoding for error correction) and the resulting encoded bits are mappedon the time-frequency resources. For example, in LTE Rel-8, thesetime-frequency resources occupy the first several OFDM symbols in asub-frame. A group of four Resource Elements is termed as a ResourceElement Group (REG). Nine REGs comprise a Control Channel Element (CCE).The encoded bits are typically mapped onto either 1 CCE, 2 CCE, 4 CCE or8 CCE. These four are typically referred to as aggregation levels 1,2,4and 8. The UE searches the different hypotheses (i.e., hypotheses on theaggregation level, DCI Format size, etc) by attempting to decode thetransmission based on allowable configurations. This processing isreferred to as blind decoding. To limit the number of configurationsrequired for blind decoding, the number of hypotheses is limited. Forexample, the UE does blind decoding using the starting CCE locations asthose allowed for the particular UE. This is done by the so-calledUE-specific search space, which is a search space defined for theparticular UE (typically configured during initial setup of a radio linkand also modified using RRC message). Similarly a common search space isalso defined that is valid for all UEs and might be used to schedulebroadcast downlink information like Paging, or Random access response,or other purposes.

The transmission of the PDCCH from the RN to the UE2 typically requires2 symbols in frames that the RN needs to receive from the eNB, forexample, non-unicast sub-frame with the first one or two (or possiblyzero) OFDM symbols being PDCCH and common RS for up to 4 or moreantennas. Assuming 1 symbol of transmit-to-receive switch gap in RN, theRN can start its reception of the sub-frame transmitted by the basestation from the 4^(th) symbol. Under this assumption, the startingposition of the floating control channel can be set as early as the4^(th) symbol. In FIG. 6, the control channel of eNB-to-RN link is FDMwith eNB-to-UE1 link. FDM enables efficient resource sharing between theeNB to RN and eNB to UE1 link. The occupied bandwidth of the controlchannel is in multiples of 12 sub-carriers, the same as the number ofsub-carriers in an RB. The RN blindly decodes control information in thesub-frame. For example, assuming “N” starting positions and “M” RBs forthe control channel, the number of blind detection will be “NM”.

The size of the floating control channel for RN may be defined similarto the REG/CCE/aggregation level as defined previously for UE1. However,it might be possible to define a new control channel structure. Forinstance, it may be advantageous to limit each control channel tosubcarriers within the first slot to reduce decoding latency. In anotherinstance, it may be advantageous to limit the control channel for a RNto small number of Resource Blocks so that the remaining Resource Blockscan be assigned to a Release-8 UE1. In yet another example, it might beadvantageous to limit the control channel for a RN to small number ofvirtual Resource Blocks thus benefitting from frequency diversity but atthe same time the remaining Resource Blocks can be assigned to a Rel-8UE. For simplicity, the other control information such a physicalcontrol format indicator channel (PCFICH), physical Hybrid-automaticrepeat request Indicator channel (PHICH), etc are left out of thisdescription, but it should be obvious to those skilled in the art thatthe different channels are multiplexed into the control region. At thispoint, it is also noted that the uplink transmissions from UE2 to RN andthe RN to eNB also need to be time-multiplexed as the RN may not be ableto simultaneously receive from UE2 while the RN is concurrentlytransmitting to eNB. It is noted that the RN can efficiently use thecontrol signaling in 1st few OFDM symbols to send appropriate schedulingmessages to reduce or minimize UE2 uplink transmissions wheneverrequired. In cases where RN is unable to inhibit UE2 uplinktransmissions such as sounding reference symbol, Random Access, Channelquality indicator (CQI), etc. and RN needs to transmit on the uplink tothe eNB, it may choose to ignore UE2 uplink transmissions, which mightlead to some additional interference. Alternatively, the RN may sendspecific message via PDCCH (broadcast or unicast) to UE2 to disabletheir uplink transmissions.

FIG. 7 shows a high-level diagram of a typical frame structure forfrequency division duplex operation (FDD). A 10 ms radio frame comprisesten downlink sub-frames and ten uplink sub-frames. Typically, theprimary broadcast control is transmitted in sub-frame 0 andsynchronization channels are sent sub-frames 0 and 5. The pagingmessages may be sent in sub-frames 0 and 5 and depending on additionalsystem capacity sub-frame 4 and sub-frame 9 may occasionally be used forpaging channel. For UEs to receive paging and system informationmessages, the sub-frames 0,5 are reserved as “normal” or “unicast”sub-frames containing common reference symbols. Some other sub-framesmay be occasionally characterized as special sub-frames or non-unicastsub-frames, for example, Multimedia Broadcast Multicast Service over aSingle Frequency Network (MBSFN) sub-frames frames, wherein thesub-frame structure is different from a unicast sub-frames. In thespecial sub-frames or non-unicast sub-frames, the first one or two (orpossibly zero) OFDM symbols may contain the PDCCH and reference symbols,whereas the rest of the sub-frame including the RS structure may bedifferent than a unicast sub-frame. For instance, the multimediamulticast broadcast over single frequency network (MBSFN) sub-frame is atype of non-unicast sub-frame. The non-unicast sub-frame may also bereferred to as a non-Release-8 sub-frame and may be used for newfeatures in future releases. Therefore, a UE that does not support MBSFNor non-unicast sub-frame may be able to save battery life by turning thetransceiver off on such sub-frames. It may also be possible to definesome sub-frames as empty or blank sub-frames. The non-unicast (orspecial sub-frame) signaling pattern may be part of system configurationor System Information Broadcast (SIB) message and may be defined on aRadio-frame level or for a group of Radio Frame level. The periodicityof MBSFN (or special sub-frame) signaling may be defined on a 8 ms or 10ms periodicity with occasional overriding by the unicast sub-frames totransmits the primary broadcast or synchronization messages. It is notedthat there may be more than one type of special sub-frame, example, anMBSFN sub-frame, blank sub-frame, etc.

FIG. 8 shows diagram of an eNB downlink transmission to one or morerelay nodes where RN1 is relay node 1 and RN2 is relay node 2. Moregenerally, RN1 may be a first group of RNs and RN2 may be a second groupof RNs. FIG. 8 also shows an example of more than one possible startinglocation for the second control region for RN1 and RN2. The RN1 decodesthe different control region to find its resource allocation. It may bepossible for an RN to receive more than one resource allocation, withsame or different time-frequency resources, in a sub-frame. This mightbe advantageous when an RN has more than one TB allocation in thesub-frame. For clarity, the possible second control regions in thefigure are represented with abbreviated notation SCR.

A Relay or RN can take advantage of the MBSFN signaling to transmit toUE2 and receive from eNB with a sub-frame. FIG. 9 shows diagram of a eNBdownlink transmission to an RN1 on the top and a corresponding RN1transmission to a UE2 on the bottom. Whenever RN1 is expecting DL datafrom the eNB in a sub-frame, RN1 signals to the UE2 that the sub-frameis an MBSFN sub-frame and hence the UE2 may read only the first one ortwo (or possibly zero) OFDM symbols from the RN1 DL transmission. RN1may be able to transmit “empty” or “blank” in the rest of the sub-frame.The blank or empty may comprise of not transmitting any referencesignals or control or data. It may also be noted that the rest of thesub-frame may include some additional transmission. It is can be seenthat the RN1 can receive the DL transmission from the eNB and search thepossible second control region to find data for RN1. Generally, RN1 maybe a first group of RNs and RN2 may be a second group of RNs.

Typically, control information is transmitted about the downlink controlinformation (DCI) formats, which inform the UE of the modulation andcoding scheme, transport block size and location, preceding information,hybrid-ARQ information, UE Identifier, etc that is required to decodethe downlink data transmissions. This control information is protectedby channel coding (typically, a cyclic-redundancy check (CRC) code forerror detection and convolutional encoding for error correction) and theresulting encoded bits are mapped on the time-frequency resources. Forexample, in LTE Rel-8, these time-frequency resources occupy the firstseveral OFDM symbols in a sub-frame. Typically in the LTE example, agroup of four Resource Elements is termed as a Resource Element Group(REG). Nine REGs comprise a Control Channel Element (CCE). The encodedbits are typically mapped onto either 1 CCE, 2 CCE, 4 CCE or 8 CCE.These four are typically referred to as aggregation levels 1,2,4 and 8.The UE searches the different hypotheses (i.e., hypotheses on theaggregation level, DCI Format size, etc) by attempting to decode thetransmission based on allowable configurations. This processing isreferred to as blind decoding. To limit the number of configurationsrequired for blind decoding, the number of hypotheses is limited. Forexample, the UE does blind decoding using the starting CCE locations asthose allowed for the particular UE. This is done by the so-calledUE-specific search space, which is a search space defined for theparticular UE (typically configured during initial setup of a radio linkand also modified using Radio Resource Configuration (RRC) message).Similarly a common search space is also defined that is valid for allUEs and might be used to schedule broadcast downlink information likePaging, or Random access response, or other purposes.

While the present disclosure and the best modes thereof have beendescribed in a manner establishing possession by the inventors andenabling those of ordinary skill to make and use the same, it will beunderstood that there are equivalents to the exemplary embodimentsdisclosed herein and that modifications and variations may be madethereto without departing from the scope and spirit of the inventions,which are to be limited not by the exemplary embodiments but by theappended claims.

1. A wireless communication relay terminal comprising: a transceiver, acontroller coupled to the transceiver, the controller configured tocause the transceiver to transmit a first portion of a first sub-frameduring a first time-frequency region to a wireless communication device,the controller configured to cause the transceiver to receive, from abase station, a portion of a second sub-frame during a secondtime-frequency region wherein the first and second time-frequencyregions are non-overlapping, the controller configured to detect acontrol region within the portion of the second sub-frame received byattempting to decode information in a possible control region of thesecond sub-frame having at least one of several possible startinglocations that are known a priori by the terminal.
 2. The terminal ofclaim 1, the controller configured to cause the transceiver to receive,from the base station, the portion of the second sub-frame during thesecond time-frequency region wherein the first and second time-frequencyregions are separated by a time interval.
 3. The terminal of claim 1,the time interval separation of the first and second time-frequencyregions is an integer number of OFDM symbols.
 4. The terminal of claim1, the time interval separation of the first and second time-frequencyregions is an integer number of time units.
 5. The terminal of claim 1,the controller configured to detect the second control region within theportion of the sub-frame received by attempting to decode information inthe possible control region having a dimension that is known a priori bythe terminal.
 6. The terminal of claim 1, the first portion of the firstsub-frame includes a physical downlink control channel.
 7. The terminalof claim 1, the first sub-frame is a non-unicast sub-frame.
 8. Theterminal of claim 1, the first sub-frame is a multimedia broadcastmulticast over a single frequency network sub-frame.
 9. The terminal ofclaim 1, the terminal decodes the possible second control region in atime interval non-overlapping a time interval corresponding to the firstcontrol region.
 10. The terminal of claim 1, the first and secondsub-frames are separate from a sub-frame containing a paging channeltransmitted by the terminal.
 11. The terminal of claim 11, the portionof the first sub-frame includes a first control region having schedulingmessages.
 12. The terminal of claim 1, the portion of the secondsub-frame includes a second control region corresponding to the possiblecontrol region having scheduling messages.
 13. The terminal of claim 12,the portion of the second sub-frame includes a data region that isdistinct in time-frequency from the second control region.
 14. Awireless communication base station comprising: a transceiver; acontroller coupled to the transceiver, the controller configured togenerate a sub-frame having first control region for a first set ofusers and a second control region for a second set of users that do notreceive the first control region, the first control region having afixed starting location within the sub-frame and the second controlregion having a starting location that is one of several possiblestarting locations within the sub-frame; the controller configured tocause the transceiver to transmit the sub-frame to the first and secondsets of users without signaling the actual starting location of thesecond control region in the sub-frame.
 15. The base station of claim14, the controller configured to cause the transceiver to signal theseveral possible starting locations of the second control region withoutsignaling the actual starting location of the second control region. 16.The base station of claim 14, the controller configured to generate thesecond control region having a fixed size that is known to the secondset of users.
 17. The base station of claim 14, the controllerconfigured to generate the second control region having a size thatcorresponds to one of several possible sizes that are known to thesecond set of users.
 18. The base station of claim 14, the controllerconfigured to generate the first control region to convey informationfor resource allocations within a traffic region of the sub-frame to thefirst set of users, the first control region and the traffic region aremultiplexed temporally, the controller configured to generate the secondcontrol region to convey information for resource allocations within thetraffic region of the sub-frame to the second set of users.
 19. The basestation of claim 18, the controller configured to temporally multiplexthe second control region and the traffic region.
 20. The base stationof claim 18, the controller configured to frequency multiplex the secondcontrol region and the traffic region.
 21. The base station of claim 18,the controller configured to temporally multiplex the first and secondcontrol regions.
 22. A wireless communication relay terminal comprising:a transceiver, the transceiver configured to receive a portion of asub-frame transmitted by a network base station, the sub-frametransmitted by the base station having a first control region with afixed starting location within the sub-frame and second control region,wherein a starting location of the second control region is at one ofseveral possible starting locations within the sub-frame, the portion ofthe sub-frame received excludes at least a portion of the first controlregion; a controller coupled to the transceiver, the controllerconfigured to detect the second control region within the portion of thesub-frame received by attempting to decode information in a possiblecontrol region having at least one of the several possible startinglocations, wherein the possible starting locations are known a priori bythe terminal.
 23. The terminal of claim 22, the controller configured todetect the second control region within the portion of the sub-framereceived by attempting to decode information in the possible controlregion having a known size.
 24. The terminal of claim 22, the terminaldecodes the possible second control region in a time intervalnon-overlapping a time interval corresponding to the first controlregion.